This application requests funds for state-of-the-art Light Scattering (LS) devices for the characterization of macromolecular size, shape, oligomeric state and solution behavior. The instrumentation will consist of a Wyatt Technology Corporation DAWN HELEOS MALS (Multi-angle static light scattering) system, a WyattQELS (Quasi-Elastic-Light-Scattering, i.e., dynamic light scattering) instrument, and a Optilab rEX refractive index detector interfaced with an Agilent HPLC for in-line, real time LS analysis of samples separated by size exclusion and other forms of chromatography. This equipment will provide analytical capabilities currently not available at Cornell, essential for over a dozen active NIH supported grants. The proposed instrument will complement existing instrumentation at Cornell, particularly with respect to analyzing intact and exchanging protein complexes, protein-protein/ligand interactions and probing protein conformation. Accurate assessment of protein size and shape is a critical first step in molecular characterization. Moreover, associating systems underlie many mechanisms of signal transduction and biological regulation. It is becoming increasingly important to delineate conformational change from complex formation. Careful analyses of heterogenous samples by separation techniques combined with MALS/DLS can achieve these goals in a time and cost effective manner. Furthermore, many other forms of structural analysis such as x-ray crystallography and NMR spectroscopy rely on identifying conditions where samples are monodisperse and homogeneous. MALS/DLS analysis will greatly enhance and accelerate our ability to screen samples for crystallization trials and other biophysical experiments. The particular strengths of the proposed instrument are 1) Direct and absolute molecular weight measurements from simultaneous 18 angle static light scattering measurements;2) Evaluation of the solution refractive index (n) and the change in refractive index with concentration (dn/dc) at the wavelength where static LS measurements are made;3) Simultaneous assessment of diffusion coefficients from intensity fluctuations;4) Sophisticated analysis software that provides standard deviations on each measurement;5) Batch or flow cell analysis for examination of small samples or coupled HPLC eluates. The acquisition of this instrument will have an important impact on more than a dozen NIH-funded research projects, and will improve the research infrastructure of Cornell University and the education/training programs of students and researchers. It will accelerate and facilitate a wide range of research projects of Cornell faculty across three colleges relevant to life sciences research, and help to maintain Cornell's competitive position.